# Number of repeating variable

1. Jun 19, 2016

### foo9008

1. The problem statement, all variables and given/known data

Is the question wrong ?

2. Relevant equations

3. The attempt at a solution
I found that the number of dimension = 6 , primary dimensionof velocity is L / T , which is 2 , number of repeating variable = 2 , so , there are 6-2 = 4 pi group , why the question only gt 3 pi group ?

Last edited: Jun 19, 2016
2. Jun 19, 2016

### foo9008

How to do this question?

3. Jun 19, 2016

### haruspex

Not sure where you get that formula from. As I understand it, you have 6 quantities that, between them, involve 3 dimensions (MLT), so the equation can be written relating 6-3=3 dimensionless expressions.